jsonpb: bring back old behaviour of handling nulls and JSONPBUnmarshaler

[krzysztofdrys]

What version of protobuf and what language are you using?
go version go1.16.2 darwin/amd64
v1.5.1

What did you do?
We are using a field with a message, which implements jsonpb. JSONPBUnmarshaler to implement NullValue like behaviour for our own messages. This is very similar to the old behaviour of TestUnmarshalNullWithJSONPBUnmarshaler (pre: cc376d7)

What did you expect to see?
When I receive null json value in a nested field, which implements jsonpb. JSONPBUnmarshaler, I expect UnmarshalJSONPB to be called.

I other words, I expect test TestUnmarshalNullWithJSONPBUnmarshaler in form pre cc376d7 to pass.

What did you see instead?

nil is assigned to this field.

I am aware that some breaking changes in similar area have been announced: https://github.com/golang/protobuf/releases#v1.4-nil-values But from what I understand, these release notes are about changes in handling nil go structures, whereas my change is about handling null json elements.

I created a pull request which resolves this issue #1300

[dsnet]

The github.com/golang/protobuf module is deprecated. We only accept changes to documentation, bugs fixes with justifiable impact, or fixes for a regression. Since this is fixing a regression, it seem appropriate to restore this functionality.

[dsnet]

#1300 has been merged. Thanks for the report and fix.

[krzysztofdrys]

Thanks @dsnet for guiding me trough the process of fixing this.

Is there any chance that this will be released soon?

[dsnet]

v1.5.2 is tagged.